A large boiler or burner comprises a plurality of nozzles used to inject a reactive mixture of hydrocarbon fuel (i.e. coal or oil or gas) and air or oxygen into a combustion chamber where heat or syngas is produced. Heretofore, three methods have been available for monitoring the combustion status of large boilers. In one method known in the art, the volume of air and the volume of coal supplied to the combustion chamber are controlled in accordance with the temperatures inside the furnace, as disclosed in U.S. Pat. No. 5,049,063 entitled "Combustion control apparatus for burner." Since the boiler is equipped with as many as 36 or more nozzles, it is impossible to determine the combustion status of the entire system and to discriminate the abnormal combustion status caused by a single nozzle or by a group of nozzles based on a localized temperature measurement inside the furnace. In another method known in the art, each nozzle is equipped with a flame detector. However, a flame detector only has a function to discriminate "fire on or off," and does not possess the function of combustion status monitoring, this method often causes an excess amount of fuel to accumulate, even to a point where there is the danger of having an uncontrolled explosion within the combustion chamber. In still another method known in the art, a combustion status monitoring system may be used comprising a CCD scan camera, a monitor and an automatic control unit. The CCD camera is used to scan the flame color of each nozzle, and the combustion status is observed by the monitor to thereby optimize the volume of supplied air and fuel. Since the CCD camera cannot be installed inside the combustion chamber due to the high temperature, the small view field of the CCD camera makes it impossible to scan the entire relevant target area inside the large chamber. On the other hand, the camera cannot distinguish the flame locations, therefore, the similar signature of the background and nearby flames often cause such systems to produce unacceptable errors and incorrect results.
It is an objective of the present invention to provide a novel combustion status monitoring system and method based on not only the measurements of temperature, but also on the flame flash frequencies and the burned fuel particle densities inside the entire combustion chamber. It is another objective of this invention to provide a relatively simple, low cost, yet highly effective and accurate combustion status monitoring system capable of monitoring the combustion status of the entire boiler by monitoring the combustion status of each nozzle.